The Effective Ways to Reduce Roll Consumption

1. Overview

The roller directly contacts the strip rolled product, which is an important tool for hot rolling production. Reducing roller consumption can effectively reduce production costs and increase benefits. At the same time, it can effectively improve the operation rate of the rolling mill and ensure the surface quality of hot rolled products. In the production of hot-rolled strip steel, the consumption of rolls is particularly huge. Therefore, it is of great significance to find out measures to reduce the roll consumption and increase the life of the rolls.

2. Optimize the roll change period

2.1 Rough rolling work roll
The original rough rolling roll changing period is 2.5wt ～ 3.8wt, on this basis, gradually extend the roll changing period, and compare the roll wear, strip shape and surface quality. The roll changing period is now stable at 3.8wt ~ 4.5wt. It does not affect the shape and surface quality of the strip, and extends the service life of the roll.

2.2 Back-up roll of finishing rolling mill
The rotation speed of F1-F7 roll is different and the difference is large, so the wear degree of back-up roll is also different. The one-cut roll change period that originally used 10wt-15wt is unreasonable, and the segmented roll change is now used.

Since the adoption of sectional roll change, not only the rolling capacity of the roll has been increased by about 14.94%. Moreover, according to the statistical data, the wave shape of the roller when rolling the thin gauge at the end of use is also reduced.

3. Correct treatment method of rolling accident

Serious rolling accident directly increases the numerical value of roll consumption, and whether the accident roll can be handled correctly after the accident is the key to reduce the roll consumption.

3.1 Stuck steel accident
In case of steel jamming, the cooling water shall be stopped immediately and the upper roll shall be lifted to avoid the upper roll contacting the strip steel; after the strip steel is removed, the roll shall be changed and cooled slowly. If the roll cannot be changed immediately and the crack is not serious, the working roll can enter into normal rolling only after the cooling water is not opened and idling for 5-10 minutes to make the temperature spread evenly.

3.2 Steel sticking accident
First remove the sticking steel. After that, the steel sticking area shall be inspected in detail, including hardness, crack, flaw detection, etc. the affected area of steel sticking must be removed to ensure that the hardness of the roll surface is uniform and free of crack.

4. Treatment method of common accident roll:

4.1 Hot cracks
Most of the hot cracks are caused by the cold and exciting heat of the roll after the accident of steel jamming or steel piling.

Treatment method: R1 and F1-F4 rolls can be rolled with hot cracks on the premise of ensuring smooth rolling, and the cracks are closed (closed cracks do not extend, but with the use of time), and the cracks will be gradually eliminated.

4.2 Roll bonding
Steel sticking on the roll, tail flicking or steel piling accidents cause the steel sticking on the roll.

Treatment method: when the thickness of the roll is more than 3mm, the adhered strip needs to be turned off first. Check the surface of the roll body after the attached sheet metal is removed. If there is any crack or peeling (peeling off), the cutting depth shall be determined according to the damage degree, so as to eliminate the defect without increasing the roll consumption.

4.3 Edge peeling of working roll
The edge of the working roll is peeling off, and the stress concentration of the shoulder of the roll is caused.

Treatment method: because the shoulder of the roll does not contact the steel plate directly, the part of the crack peeling off can be removed, the chamfer can be grinded, and the chamfer way and angle of the contact supporting roll can be adjusted to improve the stress distribution of the roll body.

4.4 Back up roll defects

The back-up roll is not in direct contact with the strip steel and its hardness is lower than that of the working roll, but its price is expensive, so it is not suitable to adopt the conventional grinding method.

Treatment method: when the damage is at the edge of the roller, increase the length of the end chamfer properly during grinding. The residual defects shall be treated with an angle grinder and the periphery shall be too smooth to prevent further spread of peeling defects. When the damage is in the middle of the roller, it should be grinded as usual and then treated with an angle grinder to make the defect too smooth.

5. Adjustment of roll shape

According to the actual production situation, the F1-F4 roll is changed from concave roll to HVC roll. Moreover, the negative crown of f5-f7 roll is increased to improve the stress distribution on the roll surface. The utility model can achieve the purpose of better controlling the plate shape and reducing roller consumption.

6. Other ways to reduce roll consumption

① Organize to drill the treatment methods of various rolling accidents, improve the emergency response speed, and minimize the damage to the roll caused by the accident;

② Set up reasonable detection standard of roller to ensure the quality of roller and reduce unnecessary loss;

③ Select excellent roll manufacturers, and customize high-quality rolls with materials and hardness in line with the production characteristics of Chongqing Iron and Steel Co., Ltd;

④ After the production is stable, the high-speed steel roll is selected for the working roll in the front section of finishing rolling to further reduce the roll consumption.

7. Conclusion

① The adjusted HVC profile and negative crown roll not only improve the stress distribution on the roll surface, but also strengthen the crown control ability of the strip steel, which is conducive to the guarantee of product quality.

② Adjusting the roll changing period, responding to the rolling accident and correctly handling the accident roll can ensure the product quality, increase the rolling amount of a single roll and extend the service life of the roll.

③ The treatment measures for the accident roll reduce the unnecessary grinding of the roll, thus reducing the labor intensity of the staff.

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